A Merck & Co. (MRK) drug for a rare type of cancer flushed out hidden deposits of HIV in a study, according to researchers who say the results provide a hint that curing AIDS may someday be possible. The finding on Merck’s Zolinza, reported today in the journal Nature, comes as researchers at the International AIDS Conference in Washington this week express optimism a cure is on the horizon. While current treatments hold the disease at bay, stopping the drugs can be a death sentence since it allows infected cells that remain hidden within the immune system to re-emerge, spreading the virus anew.